Agraph of coal reserves in the united states versus time slopes downward this indicates that coal production could have
decreased
increased
fluctuated
stayed the same

Option A.

Explanation:

It is given that a graph of coal reserves in the united states versus time slopes downward.

It means, in the graph x-axis represents the time and y-axis represents the coal reserves.

Negative slope represents the negative relation between coal reserves and time. It means coal reserves will decrease if time increases.

In other words, the downward slope indicates that coal production could have decreased.

Therefore, the correct option is A.

2fe + 3h2so4 -> fe2(so4)3 + 3h2

it is necessary to balance equations in order to get the proper amount of reactants as well as products in order not to make a miscalculation.

you cannot change the subscripts as that would change the substance itself. for instance, diatomic elements such as h2 only have the subscript two when a gas. another example would be so4, if you were to change the subscript, the element would no longer be sulfate.

we change the coefficients instead as that only changes the number of molecules rather than the substance itself.

hope this !